gallium/auxiliary: replace call to dup(2) with fcntl(F_DUPFD_CLOEXEC)
gallium/auxiliary: replace call to dup(2) with fcntl(F_DUPFD_CLOEXEC)

Without this fix, duplicated file descriptors leak into child processes.
See commit aaac913e901229d11a1894f6aaf646de6b1a542c for one instance
where the same fix was employed.

Cc: <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>
Signed-off-by: Matt Whitlock <974f068c1a0f77888ff3f4e29cc3ce5ddb2d9058@mattwhitlock.name>
Reviewed-by: Nicolai Hähnle <0d0be6cf5ad662651be2dc5dfd44aa2b09d4c1cc@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler